Veterinarians and animal house workers are being studied for the presence of allergic alveolitis, asthma and other manifestations of hypersensitivity lung disease caused by the animal antigens to which they are exposed. A control population of non-exposed, normal individuals is being studied as well. The test population is being assayed by questionnaire, physical examination and simple pulmonary function tests as well as immediate-type skin tests using the relevant antigens as part of a general screen. Serum obtained will be assayed by RAST for specific IgE antibodies and by precipitin tests for specific IgG and IgM antibodies. Those subjects demonstrating evidence of specific hypersensitivity by history or examination or allergy assay will have bronchial challenge done along with complete pulmonary function tests. All tests will be done on the control subjects except for the bronchial challenge. Follow-up studies will be done on a sample of the negative and positive subjects at two years after initial encounter. Prevalence of this problems will be established and development of hypersensitivity over the two year observation period will be characterized. From this risk will be calculated and modifying factors looked for.